Soak them in saltwater. Put enough water to cover the fish and then add some non iodized salt. I usually cook about 10 pcs. at a time and put about 2 to 3 teaspoons of salt in the water. Soak overnight.
When we can't find crappie, and really want some freshwater fish = then we do work on the sandies for 24 hours to get them to taste like crappie. But - IMHO - it IS TOO MUCH work to get them to taste good!!
Justchillin's suggestion is how my wife starts the process, then do the buttermilk soak for atleast two hours, then - batter with whatever you choose and fry them in coconut oil. Yummy - after all that work! IMHO